Zero error = + (2 × 0.01) = +0.02 mm (positive because zero is below datum, so the instrument reads too high). Observed reading = 4.00 + (45 × 0.01) = 4.00 + 0.45 = 4.45 mm. Corrected reading = Observed – Zero error = 4.45 – 0.02 = 4.43 mm . Problem 4: With Negative Zero Error When closed, the 96th division of a 100-division circular scale (LC = 0.01 mm) coincides with the datum line. A measurement gives MSR = 2.50 mm, CSR = 30. Find the true thickness.
Here, zero is above the datum line. Number of divisions below zero = 100 – 96 = 4 divisions. Zero error = – (4 × 0.01) = –0.04 mm (negative). Observed reading = 2.50 + (30 × 0.01) = 2.80 mm. Corrected reading = Observed – (Zero error) = 2.80 – (–0.04) = 2.84 mm . (Alternatively: Observed + 0.04) Problem 5: Finding Pitch from Least Count The least count of a micrometer is 0.001 cm and the circular scale has 500 divisions. What is the pitch in mm? questions on micrometer screw gauge